While combined chemotherapy and thoracic radiotherapy is the standard of care for most patients with SCLC, thoracic radiotherapy target volumes of limited-stage SCLC have been controversial. Clinicians have been uncertain as to whether to treat the prechemotherapy tumor volume or the postchemotherapy residual tumor volume. To date, this is the only prospective randomized study on these issues evaluating thoracic radiotherapy for limited-stage SCLC.

The study used three-dimensional conformal radiotherapy (3D-CRT) or intensity modulated radiotherapy (IMRT) to deliver radiotherapy to target volumes of the disease. Over the course of 15 years, 309 eligible patients were randomized to irradiate the postchemotherapy (study arm) or prechemotherapy tumor volumes (control arm). IFRT was also used for both arms.

Results

The results showed neither mediastinal lymph nodes nor primary tumors developed out-of-field recurrence. At the 1, 3, and 5-year follow-ups, local/regional progression-free probability were 79.4%, 60.1%, and 60.1%, respectively, in the study arm vs 79.8%, 64.5%, and 57.3% in the control arm. The median overall survival time was 22.1 months in the study arm and 26.9 months in the control arm.

Additionally, treatment-related toxicities were reduced in patients who received radiotherapy to the postchemotherapy tumor volume. Pathologic and radiation dosimetric analysis further demonstrated that the routine use of IFRT and radiotherapy volumes could be limited to the postchemotherapy residual primary tumor.

“Considering the high malignancy and easy metastasis of SCLC, chemotherapy remains the cornerstone of comprehensive treatment,” said Dr. Hu. “For patients having difficulty with full-dose intravenous chemotherapy, it could be administered safely by dose reduction or using single agent chemotherapy or oral chemotherapy, along with radiotherapy.”

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